Not really, this is all traffic on port 80/http. There is no proxy that is inspecting the packets to make a difference here. Also a single connection can only run at a single WAN, so unless you use a downloadmanager it won't help you with a single client and a single download. Multiple downloads or multiple clients of course can take advantage of the loadbalancing.

Please search the forum on how the multiwan does the loadbalancing. It has been extensively discussed before.